To maintain the delicate balance of good health, immune function is a vital physiological function in the human body, but one of the most amazing revelations to emerge over the past few decades has been the role of the gut flora in all aspects of immunity. Our gut flora 'communicate' with our immune system and help to ensure that it responds appropriately.

What’s that now? Our resident bacteria ‘talk’ to our immune system?

Incredible as it may seem, the answer to that is ‘Yes!’ according to the available evidence. A recent review of the available research, published in the journal Frontiers of Immunology1, concluded that our probiotic bacteria, in particular our gastro-intestinal microbiota, formed a vital part of the overall immune response in humans and all other vertebrates:

“The presence of microorganisms within any vertebrate, from fish to humans, plays a significant role in the development of immunity and further capacities on disease resistance and health status along life.1

The review goes on to explain that gut dysbiosis could potentially have ‘profound physiological and metabolic consequences at local and systemic levels’.

Hmmmm…that really brings home how important it is to keep digestive function in tip top order, and evidence suggests that supplementing with probiotics, in conjunction with a healthy diet and lifestyle, could be a major contribution to good gut health2. Healthcare professionals may already be familiar with our supplement, 'For daily immunity', but for more information about how and why probiotics could benefit immune function, then read on...

But how do probiotics interact with our immune system?

It seems weird to think that tiny organisms can influence our health, working with our bodies in synergy for a mutually beneficial relationship. It’s in the interests of our resident bacteria to keep their hosts in tip top shape, and this symbiotic relationship may have evolved because bacteria naturally did what was necessary to keep their ‘homes’ safe.

But how does this relationship work?

Well, our immune system is made up of several different areas all working together in order to address the innumerable threats to which our bodies are constantly exposed: physical injuries, pathogens in the form of harmful bacteria and viruses, toxins, foreign bodies, stress, anxiety, fear etc..

To cope with this seemingly endless myriad of enemies, the immune system is divided into separate areas: the innate immune system, and the adaptive immune system which encompasses humoral immunity and cell-mediated immunity.

Our immune system is constantly under attack

Our innate immune system is our oldest, inherited weapon, thought to have been in its current form for 500 million years, and it’s a system that we share with most other living organisms, including plants. Its strength lies in ‘barriers’, such as skin, hairs, mucous membranes, and inflammatory processes, where immune cells are sent to sites of infection or trauma. The innate immune system has a very limited 'memory' and adaptive potential, however, so will harness its sister system, the adaptive immune system, when unknown 'enemies' or new situations present.

A review of the available research, published in the journal Frontiers of Immunology1, concluded that our commensal bacteria had the potential to work as an integral part of the whole immune system: by rebalancing dysbiosis (imbalance of good and bad bacteria), displacing pathogens, increasing production of antimicrobial peptides and mucins, helping to strengthen mucosal barriers and odulating cell-mediated immune responses.

Probiotics and innate immunity

As the mucosal tissues of the mouth and the gut wall comprise some of the most important ‘barriers’ involved in innate immunity, then it’s no surprise to learn that the tiny residents of these areas can significantly influence the integrity of our immune function1.

In fact, overall, around 70% of our immune system is located in our intestines, so it’s no surprise that most healthcare practitioners maintain that ‘good health starts in the gut’. So it would appear to make very good sense to keep intestinal health in optimum condition, and evidence suggests that probiotic bacteria play a key role in this4.

If the integrity of the gut wall is compromised, this can lead to ‘inappropriate’ immune responses that we know as ‘allergies’.See Kathy's great blog post on this subject here:'Gut Bacteria, Allergies, and Probiotics'

Probiotics may help to mediate allergy symptoms in a number of ways. They may help to improve the integrity of the intestinal lining, preventing permeability of the tight junctions in the epithelial wall caused by Tumor necrosis factor alpha 5 (TNFα). TNFα is a cytokine, a cell signaling protein involved in the acute inflammatory processes that can be initiated by pathogenic microbioal infection, and this process acts to damage the epithelial lining, creating permeability. This permeability allows larger protein molecules to pass through the intestinal wall and into the bloodstream, where they are seen as unnatural ‘predators’ that can stimulate a further aggressive inflammatory response that we know as an ‘allergy’.

So probiotics can help to alleviate and prevent this situation by displacing the pathogens that originally cause the inflammation and by helping to promote the secretion of anti- inflammatory mediators involved in the healing process.

In particular, a 2015 in vitro study published in the journal Physiological Reports 5 indicated that both Bifidobacterium and Lactobacillus species had great potential in preventing intestinal permeability and reducing inflammatory responses. The probiotic bacteria were shown to prevent epithelial barrier disruption induced by TNF‐α, and promote wound repair.

Probiotics and adaptive immunity

The adaptive immune system is like the ‘brains’ of the innate immune system; innate immune function is more of a ‘one size fits all’ response with a limited memory, whereas adaptive immune responses are far more sophisticated. This is the arm of the immune system that produces specifically tailored-responses to incoming antigens, which it then ‘remembers’ long-term in case they come calling again.

Emerging evidence suggests that probiotics can influence the orientation of the adaptive immune response and the production of cytokines, though different strains appear to have either pro or anti-inflammatory effects. This illustrates the importance of strain specificity when choosing a probiotic, a concept that underpins our whole product range.

Probiotics and humoral or cell-mediated immunity

This arm of the immune system kicks in when incoming pathogens are noted, and encompasses the actions of many different cell responses, including antibodies, T-helper cells, macrophages, granulocytes and natural killer cells.Pathogens can hide out and multiply both inside and outside bodily cells, but are attacked and captured by antibodies produced by B-cells, paving the way for killer T-cells and macrophages to finish the job. In this way, the immune system prevents infections from spreading throughout the body, and amazingly, our microbiota has been shown to influence the production of these antibodies and other defensive cells3.

Do our gut bacteria influence the signals that govern cell-mediated immunity?

Autoimmune responses

In some cases, the immune system turns on itself, manifesting as a large and indistinct cluster of diseases known as ‘auto-immune diseases’. Poor gut health is being linked more and more to the development of auto-immune diseases, so early intervention including the use probiotics is thought to be helpful, as they can influence the type of responses that occur.

It’s worth remembering when you’re trying to support patients with autoimmune disorders, however, that because the probiotics DO have an interaction with the immune system, they are sometimes contraindicated in those where immunity function is very weak and unpredictable.See our FAQ When should I NOT take probiotics? for more information on this.

Are certain probiotic strains more beneficial for immunity than others?

The principle underpinning our whole product range is based around the concept of strain specificity. Research appears to indicate that this principle also extends to immune function: a recent report in the Journal of Clinical Gastroenterology reviewed the potential of probiotics for allergy prevention, and concluded that:

“The probiotic performance of strains differs; each probiotic strain is a unique organism itself with specific properties that cannot be extrapolated from other, even closely related, strains…Therefore, research activities are currently focusing on identification of specific strains with immunomodulatory potential.6

Clinical research using human test subjects is the most definitive test of the efficacy of any substance. We have some great clinical trial evidence that supports the use of some of our probiotic strains for immune function, in particular Lactobacillus acidophilus NCFM® with Bifidobacterium lactis Bl-047. You can find these strains in our 'For every day EXTRA Strength' product.

Healthcare professionals may be also interested to learn about our specific product for immunity, ‘For daily immunity’. This product contains some well-known nutritional support for immunity in the form of vitamin C and other antioxidants, Green tea extract, Grape seed extract and Pine bark extract. Antioxidants have many actions within the body, and support immune function by protecting delicate membranes and seeing off free radicals that have the potential to damage the delicate membranes. We tend to recommend this product for those who suffer from repeated infections, or where immune function may be challenged, such as in the elderly or those under stress.

But the action of the probiotics in this product are equally as important as the antioxidants. In vitro evidence conducted on the probiotic strains contained in 'For daily immunity', namely L. acidophilus UBLA-34 and B.longum UBBL-64, suggested that they were particularly effective at combating pathogens such as Listeria and Yersina, an action with profound potential for gut health and immunity8.

Probiotics – a key tool for immunity

The gut microbiome can be regarded as a metabolically active organ and modulation thereof by probiotics or prebiotics is becoming increasingly recognized as an important therapeutic option.1

So if the gut microbiota is becoming widely regarded as an ‘organ’ in its own right with a key role in immune function, and the positive effects of pro and prebiotics on the intestinal flora is reasonably undisputed, then it must follow that probiotics must play a key role in the maintenance of immune function. Of course, more research into this area is essential, as probiotic mechanisms of action are still not fully understood, but the emerging evidence is continually highlighting their importance for good overall health.

Exciting times for probiotic research!

For more on the subject of Probiotics and the immune system, see some of our other blogs here:

Bifidobacterium bifidum Rosell-71 reduces colds in new study

Different probiotic strains trigger different immune responses


1. Montalban-Arques A et al (2015) Selective Manipulation of the Gut Microbiota Improves Immune Status in Vertebrates, Frontiers in Immunology. Oct 9;6:512. doi: 10.3389/fimmu.2015.00512. eCollection 2015.

2. José E. Belizário* and Mauro Napolitano (2015),Human microbiomes and their roles in dysbiosis, common diseases, and novel therapeutic approaches, Frontiers in Microbiology. 2015; 6: 1050. Published online 2015 Oct 6. doi: 10.3389/fmicb.2015.01050

3. Pagnini et al (2010) ‘Probiotics promote gut health through stimulation of epithelial innate immunity’ Proc Natl Acad Sci U S A. 2010 Jan 5; 107(1): 454–459. Published online 2009 Dec 29. doi: 10.1073/pnas.0910307107

4. Fang et al (2000) Modulation of humoral immune response through probiotic intake. FEMS Immunol Med Microbiol. 2000 Sep;29 (1):47-52.

5. Chen‐Yu Hsieh et al, (2015) Strengthening of the intestinal epithelial tight junction by Bifidobacterium bifidum, Physiological Reports Vol. 3 no. e12327 DOI: 10.14814/phy2.12327

6. Isolauri E, Salminen S, (2008), ‘Probiotics: use in allergic disorders: a Nutrition, Allergy, Mucosal Immunology, and Intestinal Microbiota (NAMI) Research Group Report’, Journal of Clinical Gastroenterology. 2008 Jul; 42 Suppl 2:S91-6. doi: 10.1097/MCG.0b013e3181639a98.

7. Leyer GJ, et al. (2009) Probiotic effects on cold and influenza-like symptom incidences and duration in children. Official Journal of the American Academy of Pediatrics; Vol. 124, pp. 172-179

8. Laboratory analysis, Unique Biotech Ltd.,Hyderabad

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